1. Field of The Invention
The invention relates to lawn sprinklers, particularly to riser rotary sprinklers having simplified structures and satisfied spraying effects in the low flow rate.
2. The Prior Art
The conventional rotary or oscillatory lawn sprinklers include the plastic vertical type as shown in U.S. Pat. Nos. 4,898,332, 4,944,456, 4,957,240, 4,967,961, 4,986,474, 5,007,586, 5,148,990, 5,226,602 and 5,297,737, and the metal slanted type as shown in U.S. Pat. Nos. 4,907,472, 4,964,572, 4,978,070, 5,090,621, 5,209,404, 5,238,188 and 5,267,689, wherein some of the plastic type can further include a pop-up structure of a hidden nozzle head when such sprinklers are in an inoperative state. For example, in U.S. Pat. No. 5,297,737 having a plastic vertical type mechanism, a portion of the stream is redirected by a pivot deflecting plate for radially spraying. In such situation, the initiative stream should be strong enough not to fail to impel such pivot plate, whereas such strong stream results in big beads of the bounced jet from the deflecting plate and that is not desired by the original intention which requires dense fine beads uniformly dispersed. On the other hand, most metal type sprinklers are generally in the form of oscillation operation, and thus have complicated mechanisms and the corresponding higher cost. A metal type sprinkler further is possibly eroded over long term use.
Therefore, an object of the invention is to provide a rotary sprinkler which has a simpler structure and a lower cost, and also performs a uniform dispensation of the water jet even though it is in a low flow rate condition.
Another object of the invention is to provide a rotary sprinkler with a riser nozzle head for easy maintenance of the lawn field when such sprinkler is in the inoperative state.
A further object of the invention is to provide a rotary sprinkler with adjustable mechanism for controlling the water jet dispersed out of the nozzle head.